1. Field of Endeavor
The present invention relates to coal gasification and more particularly to producing hydrogen from underground coal gasification.
2. State of Technology
U.S. Pat. No. 4,356,866 issued Nov. 2, 1982 to Joseph G. Savins and assigned to Mobil Oil Corporation provides the following state of technology information, “Useful product is recovered from an underground coal seam by drilling a passage extending from the surface to a cavity formed in the floor rock below the coal seam, drilling one or more upwardly radially extending channels from the cavity forming an injection manifold-like system which extends to the interface between the floor rock and the coal seam, injecting an oxidant or oxidant gas mixture into these channels from the surface, igniting the coal where the radially extending channels connect with the base of the coal seam and recovering product gases generated by the gasification process through a plurality of surrounding production wells.”
U.S. Pat. No. 5,332,036 issued Jul. 26, 1994 to Arthur I. Shirley and assigned to The BOC Group, Inc. provides the following state of technology information, “Underground coal formations and other such carbon deposits contain natural gas components, such as the lower molecular weight hydrocarbons, due to effects of long term coalification. Coal generally has a low porosity, hence most of the coalbed gas is in the form of sorbate on the surfaces of the coal rather than being entrapped within the coal. The gas is present in the coal deposit in significant quantities; accordingly it is economically desirable to extract them for use as fuel and for other industrial purposes.”
U.S. Pat. No. 6,725,921 issued Apr. 27, 2004 to Eric Pierre de Rouffignac and assigned to Shell Oil Company provides the following state of technology information, “Hydrocarbons obtained from subterranean (e.g., sedimentary) formations are often used as energy resources, as feedstocks, and as consumer products. Concerns over depletion of available hydrocarbon resources have led to development of processes for more efficient recovery, processing and/or use of available hydrocarbon resources, for example coal. In situ processes for coal formations may be used to remove hydrocarbon materials from subterranean formations. Chemical and/or physical properties of coal within a subterranean formation may need to be changed to allow coal to be more easily removed from the subterranean formation. The chemical and physical changes may include in situ reactions that produce removable fluids, composition changes, solubility changes, phase changes, and/or viscosity changes of the hydrocarbon material within the formation. A fluid may be, but is not limited to, a gas, a liquid, an emulsion, a slurry and/or a stream of solid particles that has flow characteristics similar to liquid flow.”